Chagas' disease remains a serious public health problem in this hemisphere and considerable research is required to understand the nature of the parasitism examplified by this disease. Of particular importance are the molecular mechanisms underlying the development of the etiological agent, Trypanosoma cruzi, in its insect vector. The immediate goals of these studies are: 1) examine the lectin activities in insect vector of Chagas' disease, 2) purify and immunochemically characterize the lectins from Rhodnius prolixus, a vector of T. cruzi, 3) identify and isolate the sugar determinants present on the Trypanosome that interact with the insect lectins, 4) determine the effect of R. prolixus lectins on the development of T. cruzi in vitro and in the insect 5) contrast the interaction of T. cruzi and R. prolixus with that of the insect pathogen, T. rangeli. The rational for the present proposal is based on our previous findings that unique lectin activities of distinct carbohydrate specificities are present in R. prolixus and at the sites where T. cruzi and T. rangeli normally differentiate and multiply. These lectins interact with the trypanosomes in a strictly stage-specific manner, but not with other protozoans. Specific assays and methods involving aspects of cell biology, biochemistry and immunochemistry for most of the proposed studies have already been developed. Purification of the lectins and characterization of their specificity will employ protein and carbohydrate chemistry, affinity chromatography, HPLC and other physical methods for separation, and polyacrylamide gel and autoradiography with 125I labeled materials for analysis. The results of these studies may not only provide insights of the basic mechanisms of parasitism in the intermediate host but may also be of value in developing rational strategies for prevention, therapy and diagnosis of Chagas' disease. It should not be overlooked that these studies may reveal new classes of substances in trypanosomes and insects that may have substantial importance for fundamental investigations in cell biology and insect physiology, relevant to other important vector borne diseases.